From 1999 to 2014, the overall deaths from childhood cancer fell by 20 percent. The rate among 1- to 19-year-olds went down to 2.28 per 100,000 population, from 2.85. Adolescents 15 to 19 were the most likely to die, but their rate fell by 22 percent.

There were no significant differences in the death rates of white and black children with cancer. Among whites, the rate declined 17 percent; among blacks, 23 percent. The death rate for boys was about 30 percent higher than that for girls.

In 1999, about a third of all cancer deaths among children were caused by leukemia, and a quarter by brain cancer. By 2014, these numbers had reversed — leukemia accounted for 24.9 percent of deaths, and brain cancer 29.9 percent.

Dr. Julia Glade Bender, an associate professor of pediatrics at Columbia University Medical Center, said that the reductions in death rates were the result of lessons learned in clinical trials that had led to small changes in practice.

“Many hope for cancer breakthroughs, or cancer moonshots,” she said. “But it’s a series of well-conceived trials where we’ve studied minor changes in standards of care which add up over decades to substantial gains in survival.”

Doctors are better at prognoses, she added, ramping up treatment for children with high-risk disease while easing off chemotherapy, and its side effects, for children with milder conditions.

Although there are no magic bullets, a few new drugs have been important in improving outcomes. For example, imatinib (brand name Gleevec), originally developed to treat chronic myeloid leukemia in adults, has proved useful in treating acute lymphoblastic leukemia in children.

There has been less success in treating brain cancer. Surgery carries the risk of harming critical areas of the brain, and many drugs do not pass the blood-brain barrier. Radiation for brain cancer has substantial long-term side effects.

These days, too, almost all parents are happy to enter their children with cancer into clinical trials.

“The limitations now are not in patient desire to enter into trials, but rather the lack of open clinical trials for a number of pediatric cancers, in part due to lack of funding,” Dr. Bender said.